1. Field of the Invention:
The present invention relates to slide fasteners, and more particularly to a slide fastener stringer having a continuous strip of thermoplastic molded coupling elements attached to a stringer tape along a longitudinal edge thereof.
2. Prior Art:
Various slide fastener stringers are known in which a continuous strip of thermoplastic molded coupling elements interconnected by a pair of embedded connector threads is attached to a stringer tape along a longitudinal edge thereof. The molded coupling elements are continuously made on a die wheel having in its periphery an endless series of transverse cavities. The die wheel also has in the periphery a pair of annular grooves for receiving the connector threads intersecting the transverse cavities on opposite sides thereof. After having been bent into a U-shaped cross section, the molded coupling elements are attached to the tape by sewing stitches, a weft thread of the tape, or the like. Both the sewing stitches and the weft thread have a succession of loops disposed along one longitudinal tape edge, each loop encircling the connector threads between an adjacent pair of the coupling elements, thereby securing the coupling element to said one longitudinal tape edge. However, since the only connection between the coupling elements is the connector threads, which are too flexible, only unstable attachment of the coupling elements to the tape can be achieved. This unstable attachment produces inferior slide fastenre stringers with non-uniform spaces between the coupling elements. The prior art is exemplified by U.S. Pat. Nos. 3,414,948 and 4,033,014.